138-Copy-List-with-Random-Pointer.js

/**
 * @param {Node} head
 * @return {Node}
 */
var copyRandomList = function (head) {
    let map = new Map();
    let ptr = head;

    while (ptr) {
        // map old - new
        map.set(ptr, new Node(ptr.val, null, null));
        ptr = ptr.next;
    }

    for (const [oldptr, newptr] of map) {
        newptr.next = oldptr.next && map.get(oldptr.next);
        newptr.random = oldptr.random && map.get(oldptr.random);
    }
    return map.get(head);
};